This invention relates to a method of surface modifying a medical tubing and in particular applying a surface modifier to a polyolefin tubing to functionalize the surface of tubing for improved adhesion and to increase lubricity of the surface.
In the medical field, where beneficial agents are collected, processed and stored in containers, transported and ultimately delivered through tubes by infusion to patients, there has been a recent trend toward developing materials useful for fabricating such containers and tubing without the disadvantages of currently used materials such as polyvinyl chloride. These new materials for tubings must have a unique combination of properties, so that the tubing may be used in fluid administration sets. Among these are the materials must be optically clear, environmentally compatible, have sufficient yield strength and flexibility, have a low quantity of low molecular weight additives, and be compatible with medical solutions.
It is desirable for medical tubing to be optically transparent to allow for visual inspection of fluids in the tubing.
It is also a requirement that the tubing materials be environmentally compatible as a great deal of medical tubing is disposed of in landfills and through incineration. Further benefits are realized by using a material which is thermoplastically recyclable so that scrap generated during manufacturing may be incorporated into virgin material and refabricated into other useful articles.
For tubing that is disposed of by incineration, it is necessary to use a material that does not generate or minimizes the formation of by-products such as inorganic acids which may be environmentally harmful, irritating, and corrosive. For example, PVC may generate objectionable amounts of hydrogen chloride (or hydrochloric acid when contacted with water) upon incineration, causing corrosion of the incinerator.
To be compatible with medical solutions, it is desirable that the tubing material be free from or have a minimal content of low molecular weight additives such as plasticizers, stabilizers and the like. These components could be extracted into the therapeutic solutions that come into contact with the material. The additives may react with the therapeutic agents or otherwise render the solution ineffective.
This is especially troublesome in bio-tech drug formulations where the concentration of the drug is measured in parts per million (ppm), rather than in weight or volume percentages. Even minuscule losses of the bio-tech drug can render the formulation unusable. Because bio-tech formulations can cost several thousand dollars per dose, it is imperative that the dosage not be changed.
Polyvinyl chloride (xe2x80x9cPVCxe2x80x9d) has been widely used to fabricate medical tubings as it meets most of these requirements. However, because PVC by itself is a rigid polymer, low molecular weight components known as plasticizers must be added to render PVC flexible. As set forth above, these plasticizers may leach out of the tubing and into the fluid passing through the tubing to contaminate the fluid or to render the fluid unusable. For this reason, and because of the difficulties encountered in incinerating PVC, there is a need to replace PVC medical tubing.
Polyolefins have been developed which meet many of the requirements of medical containers and tubing, without the disadvantages associated with PVC. Polyolefins typically are compatible with medical applications because they have minimal extractability to the fluids and contents which they contact. Most polyolefins are environmentally sound as they do not generate harmful degradants upon incineration, and in most cases are capable of being thermoplastically recycled. Many polyolefins are cost effective materials that may provide an economic alternative to PVC. However, there are many hurdles to overcome to replace all the favorable attributes of PVC with a polyolefin.
For example, because of the inert nature of polyolefins, due in part to the nonpolar nature of the polymer, difficulties have been encountered in bonding the polyolefin materials to polar molecules, such as polycarbonates and acrylic polymers. Typically, medical containers such as I.V. bags are connected to a patient through a series of connected tubing that have drip chambers, Y-type injection sites, venous catheters and the like between the bag and the patient. Many of these components include rigid housings manufactured from polymers such as polycarbonates, acrylics and copolyesters. The housings have sleeves in which the tubing is inserted in a telescoping fashion to attach the tube to the housing. Therefore, it is necessary for the medical tubing to be connected to the rigid housing to form a fluid tight seal with the housings.
PVC tubing is typically secured within such housings using solvent bonding techniques. Solvent bonding requires exposing the end of the tubing to be inserted into the housing to a solvent such as cyclohexanone or methyl ethyl ketone. The solvent effectively softens or dissolves the PVC so when the tubing is inserted into the housing, a bond is formed. It is desirable that the outer tubing diameter be approximately the same dimension or slightly larger than the inner diameter of the housing to form an interference fit, as close tolerances in these dimensions assists in forming a secure bond.
Solvent bonding techniques, however, are ineffective on certain polyolefins including polyethylene. Problems have also been encountered in using adhesive bonding techniques.
One attempt at overcoming this problem was to use a two step process of applying a primer material to the surface of the tubing to be bonded followed by an adhesive. The primer was applied to the tubing when the tubing was in a solid state and when both the primer and tubing were at room temperature. Cyanoacrylate adhesives have worked with some success using this technique with a primer. However, the two step process adds an additional step to a manufacturing process which could slow down the production line and increase the labor costs. Further, primers increase the cost of the process. Third, because primers typically contain large quantities of volatile chemicals such as organic solvents, and might lead to toxicity, safety and environmental problems. Fourth, primers may limit manufacturing options as they have a limited on-part life time, i.e., the primers will lose their activities within hours after exposure to an ambient environment. Finally, prior surface coating techniques have not adequately provided for both modifying the tubing surface for both increasing the adhesive compatibility with polar adhesives while at the same time lubricating the surface of the tubing for slide clamp compatibility and medical infusion pump compatibility.
In U.S. patent application Ser. No.08/642,278, the additives were blended directly into the polyolefin material. This procedure was suitable for modifing the outer surface of monolayer and multiple layered tubing as the low molecular weight additives migrated to the outer surface of the tubing. However, one drawback encountered was that for the monolayered tubings the additives also could possibly migrate to the inner surface of the tubing where they were exposed to the infusion pathway where they could leach out into the liquids flowing through the tubing.
The present invention solves these and other problems.
The present invention provides a process for modifying the surface of a polyolefin medical tubing for increasing the compatibility of the tubing with adhesives and increasing the surface lubricity of the tubing.
The present invention provides a method for fabricating a medical tubing. The method includes the steps of: (1) providing a material selected from the group consisting of ethylene homopolymers and ethylene copolymers, wherein the ethylene copolymers are obtained by copolymerizing ethylene with a comonomer selected from the group consisting of lower alkyl olefins, lower alkyl esters of a carboxylic acid and lower alkene esters of a carboxylic acid, the lower alkyl and lower alkene each have from 3-18 carbons, or blends thereof; (2) providing an extruder with an extrusion die;
(3) extruding the material into a medical tubing; (4) providing a surface modifier solution; (5) preheating the surface modifier solution to a temperature within the range of about 30-95xc2x0 C.; and (6) applying the preheated solution onto the tubing at it exits the extrusion die when the tubing is in a molten state or a semi-molten state.
The present invention further provides a method of using a medical tubing with a pump for administering measured amounts of a beneficial fluid over time to a patient. The method includes the steps of: (1) providing a material selected from the group consisting of ethylene homopolymers and ethylene copolymers, wherein the ethylene copolymers are obtained by copolymerizing ethylene with a comonomer selected from the group consisting of lower alkyl olefins, lower alkyl esters of a carboxylic acid and lower alkene esters of a carboxylic acid, the lower alkyl and lower alkene each have from 3-18 carbons, or blends thereof; (2) providing an extruder with an extrusion die; (3) extruding the material into a medical tubing; (4) providing a surface modifier solution; (5) preheating the surface modifier solution to a temperature within the range of 30-95xc2x0 C.; (6) applying the preheated solution onto the tubing at it exits the extrusion die when the tubing is in a molten state or a semi-molten state; and (8) pumping fluid through the tubing with the pump.
The present invention further provides a method of fabricating a multilayered medical tubing including the steps of: (1) extruding a multilayered tubing having a first layer and a second layer, the first layer of an ethylene monomer copolymerized with at least one monomer selected from the group consisting of lower alkyl esters of a carboxylic acid and lower alkene esters of a carboxylic acid, the lower alkyl and the lower alkene each have from 3-10 carbons, the second layer of homopolymers and copolymers of alpha olefins, the second layer being disposed concentrically within the first layer and having a modulus of elasticity greater than a modulus of elasticity of the first layer, (2) providing a surface modifier solution; (3) preheating the surface modifier solution to a temperature within the range of 50-80xc2x0 C.; and (4) applying the preheated solution onto the tubing at it exits the extrusion die when the tubing is in a molten state or a semi-molten state.
The present invention further provides a method for fabricating medical tubing including the steps of: (1) extruding with an extruder having an extrusion die a tubing having a first layer selected from the group consisting of ethylene homopolymers and ethylene copolymers, wherein the copolymers of ethylene are an ethylene monomer copolymerized with at least one monomer selected from the group consisting of lower alkyl olefins having from 3 to 18 carbons, lower alkyl esters of a carboxylic acid, the lower alkyl having from 3 to 18 carbons, and lower alkene esters of a carboxylic acid, the lower alkene having from 3 to 18 carbons, (2) providing a surface modifier solution; (3) preheating the surface modifier solution to a temperature within the range of 50-80xc2x0 C.; (3) applying the preheated solution onto the tubing at it exits the extrusion die when the tubing is in a molten state or a semi-molten state; (4) cooling the tubing to a solid state to define an initial diameter; and (5) stretching the tubing in a direction along a longitudinal axis of the tubing to define an oriented diameter that is less than the initial diameter; and (6) heat setting of the tubing.
The process of the present invention further provides exposing the tubing to an ionizing dose of radiation to improve performance with medical infusion pumps.